JP5645435B2 - Aluminum oxide precursor sol and method for producing optical member - Google Patents

Description

  The present invention relates to an aluminum oxide precursor sol and a method for producing an optical member having antireflection performance using the same, and more specifically, suitable for stably obtaining high antireflection performance in a wide region including the visible region. The present invention also relates to a method for manufacturing optical members.

  It is known that an antireflection structure using a fine periodic structure with a wavelength equal to or smaller than the wavelength in the visible light region exhibits excellent antireflection performance in a wide wavelength region by forming a fine periodic structure with an appropriate pitch and height. ing.

  As a method for forming a fine periodic structure, coating of a film in which fine particles having a particle diameter of not more than a visible light wavelength are dispersed is known. In addition, the method of forming a fine periodic structure by pattern formation by a fine processing apparatus such as an electron beam lithography apparatus, a laser interference exposure apparatus, a semiconductor exposure apparatus, or an etching apparatus can control the pitch and height, and is excellent. It is known that a fine periodic structure having antireflection properties can be formed (Patent Document 1).

  As another method, it is also known that boehmite, which is an aluminum hydroxide oxide, is grown on a substrate to obtain an antireflection effect. In these methods, an aluminum (aluminum oxide) film formed by a liquid phase method (sol-gel method) is formed into a fine periodic structure by boehmite surface treatment by steam treatment or hot water immersion treatment to obtain an antireflection film. (Patent Document 2).

  It is known that a method of forming an antireflection film using a fine periodic structure of boehmite has a very low reflectivity due to normal incidence and can provide high antireflection properties. However, in order to maintain high antireflection properties, it is required to make the height and period of the fine periodic structure constant. In the method of forming the fine periodic structure by the vacuum film forming method, the film on a curved surface or a wide surface is required. Thickness control was difficult. On the other hand, in a method of forming an aluminum oxide film by a liquid phase method (sol-gel method) and performing a hot water immersion treatment, a fine periodic structure can be formed in various surface shapes. However, an aluminum oxide precursor sol synthesized by hydrolysis of an aluminum compound is not always stable for coating. Therefore, it has been difficult to obtain an antireflection film having a small variation in reflectance after hot water treatment after being applied evenly on a substrate.

Japanese Patent Laid-Open No. 50-70040 JP 09-202649 A

  In the liquid phase method (sol-gel method) in which the antireflection film is formed using the aluminum oxide precursor sol as described above, the aluminum oxide precursor sol that does not impair the stability for coating due to aggregation, etc. In addition, there is a demand for a method for producing a high-performance antireflection film that is simpler and has less variation.

  The present invention has been made in view of the background art as described above, and provides a highly stable aluminum oxide precursor sol for coating, and an antireflection film exhibiting high antireflection performance and low variation in reflectance. The manufacturing method of the optical member which has is provided.

An aluminum oxide precursor sol that solves the above problems includes particles containing a hydrolyzate of an aluminum compound and / or a condensate thereof as components, and a solvent, and the average particle size of the particles is 2.5 nm to 7 nm. der is, the solvent, the alcohol having 5 to 8 monovalent carbon 50 wt% to 90 wt% or less, the boiling point of 110 ° C. or higher 170 ° C. or less water-soluble solvent to the following 50 wt% 10 wt% or more characterized that you a proportion.

The manufacturing method of the optical member that solves the above problems is as follows.
(1) supplying the above-mentioned aluminum oxide precursor sol on at least one surface of the substrate;
(2) a step of spreading the aluminum oxide precursor sol on a substrate;
(3) a step of forming an aluminum oxide film by drying and / or firing the substrate;
(4) The method includes a step of forming an uneven structure of aluminum oxide boehmite by immersing the aluminum oxide film in warm water of 60 ° C. or higher and 100 ° C. or lower.

  According to the present invention, it is possible to provide an aluminum oxide precursor sol that is less likely to aggregate in a liquid and has high stability for coating. Further, by using the aluminum oxide precursor sol, it is possible to provide a method for producing an optical member having an antireflection film that exhibits high antireflection performance and has little variation in reflectance.

It is a figure which shows an example of the particle size distribution curve of the particle | grains contained in the aluminum oxide precursor sol which concerns on this invention. It is process drawing which shows one Embodiment of the manufacturing method of the optical member of this invention. It is the schematic which shows one embodiment of the optical member of this invention. It is the schematic which shows one embodiment of the optical member of this invention. It is the schematic which shows one embodiment of the optical member of this invention. It is the schematic which shows one embodiment of the optical member of this invention. 4 is a particle size distribution curve of an aluminum oxide precursor sol 5 in Example 3. FIG. 2 is a particle size distribution curve of an aluminum oxide precursor sol 1 in Comparative Example 1. 4 is a particle size distribution curve of an aluminum oxide precursor sol 7 in Comparative Example 3. It is a curve showing the relationship between the amount of catalyst water and the viscosity of the aluminum oxide precursor sols 1 to 7 in Examples 1 to 4 and Comparative Examples 1 to 3. It is a curve showing the relationship between the catalyst water amount and the average particle diameter of the aluminum oxide precursor sols 1 to 7 in Examples 1 to 4 and Comparative Examples 1 to 3. 4 is a curve showing the relationship between the amount of catalyst water and the main peak area of aluminum oxide precursor sols 1 to 7 in Examples 1 to 4 and Comparative Examples 1 to 3. 6 is a graph showing absolute reflectances of optical films having wavelengths of 400 to 700 nm in Examples 9 and 10 and Comparative Examples 9 and 10;

Hereinafter, embodiments of the present invention will be described in detail.
The aluminum oxide precursor sol according to the present invention includes particles containing a hydrolyzate of an aluminum compound and / or a condensate thereof as components, and a solvent, and the average particle size of the particles is 2.5 nm to 7 nm. It is characterized by that.

  The aluminum oxide precursor sol of the present invention can form an uneven structure of aluminum oxide boehmite when coated on a substrate, dried and then immersed in warm water. Suitable for use.

The aluminum oxide precursor sol of the present invention contains, as a main component, a hydrolyzate and / or condensate thereof obtained by contacting an aluminum compound with water in a solvent. When the aluminum compound is Al-X ₃ (X represents an alkoxyl group, an acyloxyl group, a halogen group, or a nitrate ion), the hydrolyzate is Al-X ₂ (OH), Al-X (OH) ₂ , Alternatively, it is a compound represented by Al— (OH) ₃ . In the hydrolyzate, the —OH groups or the —X group and —OH group react to form an Al—O—Al bond with the elimination of H ₂ O or XH. The resulting compound having one or more Al—O—Al bonds and having a linear structure or a branched structure is a condensate of aluminum compounds. The particles are preferably amorphous.

  The condensate is considered to exist as a gel and / or particles. Therefore, when the aluminum oxide precursor sol is measured by a dynamic light scattering method, a particle size distribution curve is obtained from the scattered light intensity. Furthermore, from each peak seen in the particle size distribution curve, the ratio of particles having an average particle diameter from the area of each peak can be determined.

The average particle size of the particles obtained from each peak seen in the particle size distribution curve of the aluminum oxide precursor sol according to the present invention is 2.5 nm or more and 7 nm or less. An aluminum oxide precursor sol having a particle diameter in the above range is excellent in coating property to a substrate and has high film thickness uniformity.
Preferably, the particle size distribution curve of the aluminum oxide precursor sol according to the present invention has at least one or more peaks having a single peak, and the average particle diameter of one of the peaks is 2.5 nm or more and 7 nm or less. In addition, the area of the peaks having an average particle diameter of 2.5 nm or more and 7 nm or less is 90% or more with respect to the total area of the particle size distribution curve. More preferably, it is 98% or more.

  FIG. 1 is a diagram showing an example of a particle size distribution curve of particles contained in an aluminum oxide precursor sol according to the present invention. In the particle size distribution curve in FIG. 1, the horizontal axis represents the particle diameter in logarithm, and the vertical axis represents the scattering intensity. This particle size distribution curve has two peaks, a peak with peak 1 and a peak with peak 2. A represents the average particle diameter of the peak having peak 1 and B represents the average particle diameter of the peak having peak 2. The particles in the aluminum oxide precursor sol in the present invention have an average particle diameter A of peaks having a peak 1, and are in the range of 2.5 nm to 7 nm, preferably 3 nm to 6 nm. In addition, the ratio of the area of the peak having peak 1 is preferably 90% or more with respect to the sum of the areas of the peaks having peak 1 and peak 2, that is, the total area of the particle size distribution curve.

  Although the hydrolysis condensate of an aluminum compound appears as a peak having a single peak 1, it forms a slightly insoluble matter as a by-product upon contact with water. A broad peak extending from several hundred nm to several tens of μm, which is thought to be derived from this insoluble matter, is observed as a peak having peak 2.

  The hydrolyzed condensate in the aluminum oxide precursor sol is a fine gel at the beginning of growth, and becomes particles when grown further. At the initial stage where the morphological change from gel to particles occurs, the particle size is around 2 nm and no large increase in particle size occurs. However, as the form changes from gel to particles, the gels hardly aggregate and the viscosity of the aluminum oxide precursor sol decreases. When the change from the sol to the particles completely proceeds, the particle diameter starts to increase, and the viscosity of the aluminum oxide precursor sol takes a minimum value. The particle diameter in the region where the viscosity is minimized is about 2.5 nm, and when the particle grows further, the viscosity of the aluminum oxide precursor sol increases as the particle diameter increases. When the particle diameter exceeds 7 nm, the growth of particles accelerates, the particle diameter increases rapidly, and aggregation tends to occur. That is, the condensate in the aluminum oxide precursor sol grows to some extent and becomes a state of particles in which aggregation is unlikely to occur, and the state until it further grows and tends to occur again is an average particle size of 2.5 nm to 7 nm. The range is as follows.

  When an aluminum oxide film is formed using the aluminum oxide precursor sol of the present invention and heated with water, it is more antireflective than when an aluminum oxide precursor sol containing 90% or more of particles having an average particle diameter of less than 2.5 nm is used. An antireflection film having excellent characteristics can be obtained. Furthermore, since particles with an average particle diameter of less than 2.5 nm are not sufficiently developed, there are many by-products that float with the gel-like substance in the aluminum oxide precursor sol, especially those derived from by-products that extend from several hundred nm to several tens of μm. Broad peaks remain after filtration through the membrane filter. Such an aluminum oxide precursor sol is not preferable because it is unstable as a coating solution. On the other hand, particles having an average particle diameter of more than 7 nm have a stronger cohesion force between particles, so that independent particles and aggregated particles are mixed. When many agglomerated particles are contained, the filter is clogged during filtration. Even when there are few agglomerated particles, the viscosity of the aluminum oxide precursor sol is high, and agglomeration progresses from coating to touch drying, causing a sudden increase in viscosity.

Also, when the aluminum oxide precursor sol contains a lot of by-products and aggregates and the area of broad peaks derived from the by-products extending from 100 nm to several tens of μm is 10% or more, an aluminum oxide film is formed. If treated with warm water, the reflectance may not be stable.
For the aluminum oxide precursor sol, a small amount of a metal compound composed of at least one of each of Zr, Si, Ti, Zn, and Mg can be used together with the aluminum compound. As these metal compounds, respective metal alkoxides, metal salt compounds such as chlorides and nitrates can be used. It is particularly preferable to use a metal alkoxide for the reason that the by-product during preparation of the sol has a small influence on the film forming property during coating. Further, the amount of the aluminum compound contained in the total amount of the metal compound of 100 mol% is preferably 90 mol% or more.

  The content of particles containing the hydrolyzate of the aluminum compound and / or the condensate thereof as a component in the aluminum oxide precursor sol of the present invention is 1% by weight or more and 7% by weight or less in terms of metal oxide. Preferably, it is 2.5 to 6% by weight.

Specific examples of metal compounds such as aluminum compounds are exemplified below.
Examples of the aluminum compound include aluminum ethoxide, aluminum isopropoxide, aluminum-n-butoxide, aluminum-sec-butoxide, aluminum-tert-butoxide, aluminum acetylacetonate, and oligomers thereof, aluminum nitrate, aluminum chloride, Examples include aluminum acetate, aluminum phosphate, aluminum sulfate, and aluminum hydroxide.

  Specific examples of the zirconium alkoxide include zirconium tetramethoxide, zirconium tetraethoxide, zirconium tetra n-propoxide, zirconium tetraisopropoxide, zirconium tetra n-butoxide, zirconium tetra t-butoxide and the like.

As the silicon alkoxide, various compounds represented by the general formula Si (OR) ₄ can be used. R may be the same or different lower alkyl group such as methyl group, ethyl group, propyl group, isopropyl group, butyl group and isobutyl group.

  Examples of the titanium alkoxide include tetramethoxy titanium, tetraethoxy titanium, tetra n-propoxy titanium, tetraisopropoxy titanium, tetra n-butoxy titanium, and tetraisobutoxy titanium.

Examples of the zinc compound include zinc acetate, zinc chloride, zinc nitrate, zinc stearate, zinc oleate, and zinc salicylate, with zinc acetate and zinc chloride being particularly preferred.
Examples of the magnesium compound include magnesium alkoxides such as dimethoxy magnesium, diethoxy magnesium, dipropoxy magnesium and dibutoxy magnesium, magnesium acetylacetonate, magnesium chloride and the like.

  Among the above metal compounds, aluminum-n-butoxide, aluminum-sec-butoxide, zirconium tetraisopropoxide, zirconium tetra-n-butoxide, tetramethoxysilane, tetraethoxysilane, tetraisopropoxytitanium, tetran-butoxytitanium, di A metal alkoxide such as propoxymagnesium or dibutoxymagnesium is preferably used as a raw material.

  Among the metal compounds, aluminum, zirconium, and titanium alkoxides are particularly highly reactive with water, and are rapidly hydrolyzed by the addition of water and water in the air, resulting in cloudiness and precipitation of the solution. In addition, aluminum salt compounds, zinc salt compounds, and magnesium salt compounds are difficult to dissolve with only an organic solvent, and the stability of the solution is low. In order to prevent these, it is preferable to add a stabilizer to stabilize the solution.

  Examples of the stabilizer include β-diketone compounds such as acetylacetone, dipyrobaylmethane, trifluoroacetylacetone, hexafluoroacetylacetone, benzoylacetone, and dibenzoylmethane. Methyl acetoacetate, ethyl acetoacetate, allyl acetoacetate, benzyl acetoacetate, acetoacetate-iso-propyl, acetoacetate-tert-butyl, acetoacetate-iso-butyl, acetoacetate-2-methoxyethyl, 3-keto-n Β-ketoester compounds such as methyl valeric acid. Furthermore, alkanolamines such as monoethanolamine, diethanolamine, and triethanolamine can be exemplified.

  Although the addition amount of a stabilizer changes with kinds of metal compound, 0.2 mol or more and 2 mol or less are preferable with respect to 1 mol of aluminum alkoxides. In addition, the stabilizer is effective by mixing with the alkoxide for a certain period of time before adding water.

  In order to cause hydrolysis, it is necessary to add an appropriate amount of water. The amount of water added varies depending on the solvent and concentration. The amount of water added is preferably 1.2 mol or more and less than 2 mol with respect to 1 mol of the aluminum compound.

Moreover, a catalyst can be added to water for the purpose of promoting a part of the hydrolysis reaction. It is preferable to use hydrochloric acid, phosphoric acid or the like as a catalyst at a concentration of 0.1 mol / L or less.
The solvent may be an organic solvent in which a raw material such as an aluminum compound is uniformly dissolved and particles do not aggregate. For example, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methylpropanol, 1-pentanol, 2-pentanol, cyclopentanol, 2-methylbutanol, 3-methylbutanol, 1-hexanol, 2-hexanol, 3-hexanol, 4-methyl-2-pentanol, 2-methyl-1-pentanol, 2-ethylbutanol, 2,4-dimethyl-3-pentanol, 3-ethylbutanol Monohydric alcohols such as 1-heptanol, 2-heptanol, 1-octanol and 2-octanol: Divalent or higher alcohols such as ethylene glycol and triethylene glycol: methoxyethanol (boiling point 125 ° C.), ethoxyethanol ( Boiling point 136 ° C), propoxy Tanol (boiling point 151 ° C), isopropoxyethanol (boiling point 141 ° C), butoxyethanol (boiling point 170 ° C), 1-methoxy-2-propanol (boiling point 120 ° C), 1-ethoxy-2-propanol (boiling point 132 ° C), Glycol ethers such as 1-propoxy-2-propanol (boiling point 140 to 160 ° C.): ethers such as dimethoxyethane, diglyme, tetrahydrofuran, dioxane, diisopropyl ether, cyclopentyl methyl ether: ethyl formate, ethyl acetate, n-acetate Estes such as butyl, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate Class: Various aliphatic or alicyclic hydrocarbons such as n-hexane, n-octane, cyclohexane, cyclopentane, and cyclooctane: Various aromatic hydrocarbons such as toluene, xylene, and ethylbenzene: Various ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone: Various chlorinated hydrocarbons such as chloroform, methylene chloride, carbon tetrachloride, and tetrachloroethane: N-methylpyrrolidone, N, N-dimethylform Examples include an aprotic polar solvent such as amide, N, N-dimethylacetamide, and ethylene carbonate.

  Among the above solvents, monohydric alcohols having 5 or more and 8 or less carbon atoms are preferable in that the solubility of the aluminum compound is high and it is difficult to absorb moisture. When the hydrolysis of the aluminum compound proceeds due to moisture absorption by the solvent, it becomes difficult to control the particle size. Also, moisture absorption during coating causes particle aggregation and impairs the stability of optical properties. Further, when a general low boiling point alcohol is used, the solvent evaporates quickly, and the stabilizer described above remains in the film, which affects the optical characteristics. However, a monohydric alcohol having 5 to 8 carbon atoms is used. In addition, since the solvent volatilizes with the stabilizer during drying and / or firing, the stabilizer hardly remains. On the other hand, the monohydric alcohol having 5 or more and 8 or less carbon atoms has high hydrophobicity, and water necessary for hydrolysis cannot be uniformly mixed, and it is difficult to make the particle size constant. Therefore, it is preferable to use a water-soluble solvent in combination with a monohydric alcohol having 5 to 8 carbon atoms. The water-soluble solvent described here refers to a solvent having a solubility of water in a solvent at 23 ° C. of 80% by weight or more.

The content of the solvent contained in the aluminum oxide precursor sol of the present invention is 50% by weight to 98% by weight, preferably 60% by weight to 93% by weight.
As a mixing ratio of the solvent, a monohydric alcohol having 5 to 8 carbon atoms is 50% by weight to 90% by weight, and a water-soluble solvent having a boiling point of 110 ° C. to 170 ° C. is 10% to 50% by weight. It is preferable to contain by a ratio. The water-soluble solvent is a water-soluble solvent having a boiling point of 110 ° C. or higher and 170 ° C. or lower. When a water-soluble solvent having a boiling point of less than 110 ° C. is used, moisture absorption and whitening are likely to occur due to volatilization. If a water-soluble solvent having a boiling point exceeding 170 ° C. is used, it remains in the aluminum oxide film even after drying, resulting in a variation in reflectance. It is preferable that the water-soluble solvent is glycol ether.

  In preparing the aluminum oxide precursor sol of the present invention, heating can be performed to promote the hydrolysis and condensation reaction of the aluminum alkoxide. Although the heating temperature depends on the boiling point of the solvent, it is preferably 60 ° C. or higher and 150 ° C. or lower. By heating, the particles grow and the particle properties are improved.

The method for producing the optical member of the present invention will be described in detail.
The method for producing an optical member according to the present invention includes:
(1) supplying the aluminum oxide precursor sol on at least one surface of a substrate;
(2) a step of spreading the aluminum oxide precursor sol on a substrate;
(3) a step of forming an aluminum oxide film by drying and / or firing the substrate;
(4) The method includes a step of forming an uneven structure of aluminum oxide boehmite by immersing the aluminum oxide film in warm water of 60 ° C. or higher and 100 ° C. or lower.

The steps (1) to (4) are included in order, and the aluminum oxide precursor sol is used in the step of supplying the aluminum oxide precursor sol.
It is preferable that the optical member has an antireflection film composed of a plate crystal layer formed of a plate crystal containing aluminum oxide boehmite as a component on at least one surface of the substrate.

FIG. 2 is a process diagram showing an embodiment of the method for producing an optical member of the present invention.
FIG. 2A shows a state where the above-described aluminum oxide precursor sol 2 is supplied to the substrate 1 in the step (1). The method of supplying the aluminum oxide precursor sol 2 includes a method of supplying the aluminum oxide precursor sol 2 by dropping it from a narrow tube or one or a plurality of pores, and an aluminum oxide precursor on the substrate 1 through a slit. Examples thereof include a method of attaching the sol 2 or a method of once attaching the aluminum oxide precursor sol 2 to the plate and then transferring it to the substrate 1. Moreover, the sol 2 can be supplied to the base material 1 by immersing the base material 1 in the aluminum oxide precursor sol 2.

  It is preferable to filter the aluminum oxide precursor sol in advance before feeding onto the substrate. By using a membrane filter having pores of 1 μm or less for filtration, foreign particles can be removed and large particles contained in a few percent. Examples of the filtration method include suction filtration, pressure filtration, and circulation filtration through which the filter is repeatedly passed. Moreover, in the method of supplying to a base material through the thin tube mentioned above, a sol can also be supplied, providing a filter in the middle of a thin tube, and filtering.

  FIG. 2B shows a state in which the aluminum oxide precursor sol 2 supplied in the step (1) is spread on the substrate 1 in the step (2). As a method of spreading the aluminum oxide precursor sol 2 on the substrate 1, a spin coating method that spreads the dropped sol 2 by rotating the substrate 1, a sol dropped by moving a blade or a roll on the substrate 1 For example, a blade coating method or a roll coating method can be used. Further, the aluminum oxide precursor sol 2 can be expanded while being supplied. While supplying the aluminum oxide precursor sol 2 from the slit, the slit coating method in which the slit or substrate 1 is moved to spread the sol 2 or the sol 2 once adhered to the plate is transferred while moving the plate or substrate 1. Printing method.

  A dip coating method in which the substrate 1 is once immersed in the aluminum oxide precursor sol 2 and then the substrate 1 is pulled up at a constant speed is also an example. When an optical member having a three-dimensionally complicated shape such as a concave surface is manufactured, the spin coating method is preferable because it is difficult to access the supply source of the aluminum oxide precursor sol 2.

  FIG. 2C shows a state in which the aluminum oxide film 3 is formed by drying and / or firing the substrate 1 in the step (3). When the substrate 1 is heated and dried, the aluminum oxide precursor sol 2 spread on the substrate 1 in the step (2) volatilizes the solvent, and the aluminum oxide film 3 in which particles in the sol 2 are deposited is formed. The Further heating causes volatilization of the stabilizer and condensation reaction of unreacted alkoxide and hydroxyl group. The heating temperature is preferably 150 ° C. or higher, which is necessary for volatilization of the stabilizer, and preferably 300 ° C. or lower in consideration of the influence on the base material and other members. Examples of the heating method include a method of heating in a hot air circulating oven, a muffle furnace, an IH furnace, a method of heating with an IR lamp, and the like.

  FIG. 2D shows a state in which the layer 4 having the uneven structure 5 of aluminum oxide boehmite is formed on the substrate 1 in the step (4). The concavo-convex structure 5 is formed by contacting the aluminum oxide film 3 obtained in the step (3) with warm water of 60 ° C. or more and 100 ° C. or less. The formed layer 4 having a concavo-convex structure of aluminum oxide boehmite consists of crystals of aluminum oxide or hydroxide or hydrates thereof, and the main crystals are boehmite. Examples of the method of bringing the aluminum oxide film 3 into contact with warm water include a method of immersing the base material 1 in warm water, a method of bringing warm water into running water or mist, and contacting the aluminum oxide film 3.

  The layer 4 having the concavo-convex structure 5 of aluminum oxide boehmite is preferably a plate-like crystal layer formed from a plate-like crystal composed mainly of aluminum oxide boehmite. FIG. 3 shows a schematic schematic cross-sectional view showing the optical member according to the present embodiment in that case.

  In FIG. 3, in the optical member obtained by the manufacturing method of the present invention, a plate-like crystal layer 6 made of plate-like crystals containing aluminum oxide boehmite as a main component is laminated on a substrate 1. The plate-like crystal layer 6 mainly composed of aluminum oxide boehmite is formed from crystals of aluminum oxide or hydroxide or hydrates thereof, and is mainly boehmite. The plate-like crystal layer 6 has a concavo-convex structure of aluminum oxide boehmite formed by applying the aluminum oxide precursor sol of the present invention on a substrate and bringing the aluminum oxide film formed by heating into contact with warm water. It is a layer having. In the plate-like crystal layer 6, amorphous aluminum oxide may remain in the lower portion (root portion) of the plate-like crystal.

  In addition, by arranging these plate crystals, the end portions form fine uneven shapes 7, so that the plate crystals are selectively selected in order to increase the height of the fine unevenness and narrow the interval. It is arranged at a specific angle with respect to the surface of the substrate.

  In the case where the surface of the substrate 1 is a flat surface such as a flat plate, a film or a sheet, as shown in FIG. It is desirable that the average angle of the angle θ1 is 45 ° or more and 90 ° or less, preferably 60 ° or more and 90 ° or less.

  When the surface of the substrate 1 has a two-dimensional or three-dimensional curved surface, as shown in FIG. 5, the plate-like crystal is relative to the surface of the substrate, that is, the inclination direction 8 of the plate-like crystal and the base. It is desirable that the average angle of the angle θ2 between the material surface and the tangent line 9 is 45 ° or more and 90 ° or less, preferably 60 ° or more and 90 ° or less.

  The layer thickness of the plate crystal layer 6 is preferably 20 nm or more and 1000 nm or less, and more preferably 50 nm or more and 1000 nm or less. When the layer thickness for forming the unevenness is 20 nm or more and 1000 nm or less, the antireflection performance by the fine uneven structure is effective, and the mechanical strength of the uneven structure is eliminated, and the manufacturing cost of the fine uneven structure is advantageous. Become. In addition, when the layer thickness is 50 nm or more and 1000 nm or less, the antireflection performance is further improved, which is more preferable.

  The surface density of the fine irregularities of the present invention is also important, and the average surface roughness Ra ′ value obtained by expanding the corresponding centerline average roughness is 5 nm or more, more preferably 10 nm or more, more preferably 15 nm or more and 100 nm or less, The surface area ratio Sr is 1.1 or more. More preferably, it is 1.15 or more, More preferably, it is 1.2 or more and 3.5 or less.

  As one of the evaluation methods for the obtained fine uneven structure, there is observation of the surface of the fine uneven structure with a scanning probe microscope, and the average surface roughness Ra ′ obtained by extending the center line average roughness Ra of the film by the observation. The value and the surface area ratio Sr are determined. That is, the average surface roughness Ra ′ value (nm) is obtained by applying the centerline average roughness Ra defined in JIS B 0601 to the measurement surface and extending it three-dimensionally. The absolute value of the deviation up to the average value ”is expressed by the following equation (1).

Ra ′: average surface roughness value (nm),
S ₀ : Area when the measurement surface is ideally flat, | X _R −X _L | × | Y _T −Y _B |, F (X, Y): High at the measurement point (X, Y) X is the X coordinate, Y is the Y coordinate,
X _L to X _R : X coordinate range of the measurement surface,
Y _B to Y _T : Y coordinate range of the measurement surface,
Z ₀ : Average height in the measurement plane.

The surface area ratio Sr is Sr = S / S ₀ [S ₀ : Area when the measurement surface is ideally flat. S: Surface area of the actual measurement surface. ]. The actual surface area of the measurement surface is obtained as follows. First, it is divided into minute triangles composed of the three closest data points (A, B, C), and then the area ΔS of each minute triangle is obtained using a vector product. ΔS (ΔABC) = [s (s−AB) (s−BC) (s−AC)] 0.5 [where AB, BC, and AC are the lengths of each side, and s≡0.5 ( AB + BC + AC)], and the sum of ΔS is the surface area S to be obtained. When the surface density of the fine irregularities is Ra ′ is 5 nm or more and Sr is 1.1 or more, antireflection by the irregular structure can be expressed. If Ra ′ is 10 nm or more and Sr is 1.15 or more, the antireflection effect is higher than that of the former. When Ra ′ is 15 nm or more and Sr is 1.2 or more, the performance can withstand actual use. However, when Ra ′ is 100 nm or more and Sr is 3.5 or more, the effect of scattering by the concavo-convex structure is superior to the antireflection effect, and sufficient antireflection performance cannot be obtained.

  Between the base material 1 and the layer 4 having the concavo-convex structure 5 of aluminum oxide boehmite, a layer mainly composed of components other than aluminum oxide can be provided. FIG. 6 shows an example of an optical member in which a layer 10 mainly composed of components other than aluminum oxide is formed on a substrate 1, and a layer 4 having an uneven structure 5 of aluminum oxide boehmite is formed thereon.

  The layer 10 whose main component is other than aluminum oxide is provided mainly for the purpose of adjusting the refractive index difference between the substrate 1 and the layer 4 having the concavo-convex structure 5 of aluminum oxide boehmite. Therefore, it is preferable that the layer 10 whose main component is other than aluminum oxide is a transparent film made of an inorganic material or an organic material.

Examples of the inorganic material used for the layer 10 whose main component is other than aluminum oxide include metal oxides such as SiO ₂ , TiO ₂ , ZrO ₂ , ZnO, and Ta ₂ O ₅ . Examples of the method for forming the layer 10 mainly composed of an inorganic material other than aluminum oxide include a vacuum film forming method such as vapor deposition and sputtering, and a sol-gel method by applying a metal oxide precursor sol.

  On the other hand, examples of organic materials used for the layer 10 mainly composed of other than aluminum oxide include acrylic resin, epoxy resin, oxetane resin, maleimide resin, melamine resin, benzoguanamine resin, phenol resin, resol resin, polycarbonate, polyester, Examples include organic polymers such as polyarylate, polyether, polyurea, polyurethane, polyamide, polyamideimide, polyimide, polyketone, polysulfone, polyphenylene, polyxylylene, and polycycloolefin. Examples of a method for forming the layer 10 mainly composed of an organic material other than aluminum oxide include a wet coating method in which the solution is mainly formed by coating.

In addition, the surface of the concavo-convex structure 5 of aluminum oxide boehmite can be treated to such an extent that the antireflection property is not impaired. In order to impart scratch resistance and antifouling properties, an example in which a very thin layer of SiO ₂ thin film, FAS (fluorinated alkylsilane) or fluororesin is provided can be given.

  Hereinafter, the present invention will be described specifically by way of examples. However, the present invention is not limited to such examples. The optical film having fine irregularities on the surface obtained in each example and comparative example was evaluated by the following method.

(1) Preparation of aluminum oxide precursor sols 1 to 7 17.2 g of aluminum-sec-butoxide (ASBD, manufactured by Kawaken Fine Chemical), 4.56 g of 3-oxobutanoic acid ethyl ester, and 4-methyl-2- The mixture was stirred with pentanol until uniform. After 0.01M dilute hydrochloric acid was dissolved in a mixed solvent of 4-methyl-2-pentanol / 1-ethoxy-2-propanol (boiling point 132 ° C.), it was slowly added to the aluminum-sec-butoxide solution and stirred for a while. . The solvent was finally adjusted to be a mixed solvent of 53 g of 4-methyl-2-pentanol and 23 g of 1-ethoxy-2-propanol. Furthermore, the aluminum oxide precursor sol was prepared by stirring in an oil bath at 120 ° C. for 2 to 3 hours or more. Aluminum oxide precursor sols 1 to 7 in which the amount of 0.01 M dilute hydrochloric acid was changed stepwise from 0.88 to 2.02 g were prepared.

(2) Preparation of aluminum oxide precursor sols 8 to 11 24.6 g of aluminum-sec-butoxide (ASBD, manufactured by Kawaken Fine Chemical Co., Ltd.), 6.51 g of 3-oxobutanoic acid ethyl ester, and 1-pentanol The mixture was mixed and stirred until it became cloudy at first but became homogeneous. After 0.01M dilute hydrochloric acid was dissolved in a mixed solvent of 1-pentanol / 1-ethoxy-2-propanol, it was slowly added to the aluminum-sec-butoxide solution and stirred for a while. The solvent was finally adjusted to be a mixed solvent of 49 g of 1-pentanol and 21 g of 1-ethoxy-2-propanol. Furthermore, the aluminum oxide precursor sol was prepared by stirring in an oil bath at 120 ° C. for 2 to 3 hours or more. Aluminum oxide precursor sols 8 to 11 having different amounts of 0.01M dilute hydrochloric acid from 1.8 g, 2.25 g, 2.7 g, and 3.06 g were prepared.

(3) Preparation of aluminum oxide precursor sol 12. 17.2 g of aluminum-sec-butoxide (ASBD, manufactured by Kawaken Fine Chemical Co., Ltd.), 4.56 g of 3-oxobutanoic acid ethyl ester, and 2-propanol are homogenized. Until mixed. 1.26 g of 0.01 M dilute hydrochloric acid was dissolved in 2-propanol, and then slowly added to the aluminum-sec-butoxide solution, followed by stirring for a while. 2-propanol was finally adjusted to 76 g. Furthermore, the aluminum oxide precursor sol 12 was prepared by refluxing in an oil bath for 2 to 3 hours or more.

(4) Viscosity measurement A cone plate type rotational viscometer (RE-105L, manufactured by Toki Sangyo Co., Ltd.) equipped with a standard rotor (1 ° 34 ′, R24) was used to measure the viscosity at 25 ° C. and 50 rpm.

(5) Particle size distribution measurement Using a particle size distribution meter (Zetasizer Nano S, manufactured by Malvern), about 1 ml of aluminum oxide precursor sol was placed in a glass cell and measured at 25 ° C. The analysis was conducted with the refractive index of 1.5, the absorption of 0.01, and the solution viscosity as the above measured viscosity.

(6) Cleaning of base material Only one side is polished, and the other side is ground glass-like size about φ30 mm, thickness about 1 mm disk-shaped glass substrate ultrasonically washed in an alkaline detergent and then dried in an oven .

(7) Reflectance measurement Using an absolute reflectance measuring device (USPM-RU, manufactured by Olympus), reflectance measurement was performed at an incident angle of 0 ° in the range of 400 nm to 700 nm.

(8) Surface observation of substrate The substrate surface was subjected to Pd / Pt treatment, and surface observation was performed at an acceleration voltage of 2 kV using FE-SEM (S-4800, manufactured by Hitachi High-Tech).

Examples 1 to 4
Viscosity measurement and particle size distribution measurement of the aluminum oxide precursor sols 3 to 6 were performed. The results are shown in Table 1. A particle size distribution curve in Example 3 using the aluminum oxide precursor sol 5 is shown in FIG. Further, the molar equivalent of the catalyst water (0.01M dilute hydrochloric acid) and the viscosity, the average particle diameter of the main peak, and the area% of the main peak are plotted in graphs for each of aluminum-sec-butoxide. Indicated.

Example 5
An appropriate amount of the aluminum oxide precursor sol 3 is dropped onto the polished surface of a glass substrate (φ30 mm) with nd = 1.77 and νd = 50, the main component of which is washed La ₂ O ₅ , and spin-coated at 3500 rpm for 20 seconds. went. At that time, no unevenness due to spin coating was observed. Then, it baked for 120 minutes in 200 degreeC hot-air circulation oven, and coat | covered the amorphous aluminum oxide film on the glass substrate.

Next, after being immersed in warm water of 80 ° C. for 30 minutes, it was dried at 60 ° C. for 15 minutes.
When the FE-SEM observation of the obtained film surface was performed, a fine concavo-convex structure in which plate crystals mainly composed of aluminum oxide were randomly and intricately complicated was observed.

  When the reflectance was measured, the reflectance at one central portion and two peripheral portions was measured, and the presence or absence of variation was confirmed from the magnitude of the difference in reflectance at 600 nm. As a result, the difference in reflectance was less than 0.1%, and it was confirmed that the variation in antireflection properties was small.

Example 6
The same operation as in Example 5 was performed except that the aluminum oxide precursor sol 3 was changed to 4.
As a result, no unevenness was observed during spin coating. The difference in reflectance after immersion in warm water was less than 0.1%, and it was confirmed that the variation in antireflection properties was small.

Example 7
The same operation as in Example 5 was performed except that the aluminum oxide precursor sol 3 was changed to 5.
As a result, no unevenness was observed during spin coating. The difference in reflectance after immersion in warm water was less than 0.1%, and it was confirmed that the variation in antireflection properties was small.

Example 8
The same operation as in Example 5 was performed except that the aluminum oxide precursor sol 3 was changed to 6.
As a result, no unevenness was observed during spin coating. The difference in reflectance after immersion in warm water was less than 0.1%, and it was confirmed that the variation in antireflection properties was small.

Example 9
A glass substrate (φ30 mm) having nd = 1.77 and νd = 50 mainly composed of La ₂ O ₅ obtained by washing aluminum oxide precursor sol 10 (average particle diameter and peak area are 3.5 nm and 93%, respectively). An appropriate amount was dropped on the polished surface of the film and spin-coated at 3000 rpm for 20 seconds. Then, it baked for 120 minutes in 200 degreeC hot-air circulation oven, and coat | covered the amorphous aluminum oxide film on the glass substrate.

Next, after being immersed in warm water of 80 ° C. for 30 minutes, it was dried at 60 ° C. for 15 minutes.
When the FE-SEM observation of the obtained film surface was performed, a fine concavo-convex structure in which plate crystals mainly composed of aluminum oxide were randomly and intricately complicated was observed.
The result of measuring the reflectance is shown in FIG. The effect of lowering the reflectivity by increasing the particle diameter was confirmed.

Example 10
The same operation as in Example 9 was performed except that the aluminum oxide precursor sol 10 was changed to 11 (average particle diameter and peak area were 6.8 nm and 96%, respectively).
The result of measuring the reflectance is shown in FIG. The effect of lowering the reflectivity by increasing the particle diameter was confirmed.

Comparative Examples 1 to 4
Each of the aluminum oxide precursor sols 1, 2, 7, and 12 was measured for viscosity and particle size distribution. The results at that time are shown in Table 1. 8 and 9 show the particle size distribution curves of Comparative Examples 1 and 3 using the aluminum oxide precursor sol 1 or 7, respectively. For sols 1, 2 and 7, the molar equivalent of catalyst water (0.01M dilute hydrochloric acid) and viscosity, the average particle diameter of main peaks, and the area percentage of main peaks are plotted in graphs for aluminum-sec-butoxide. 10 to 12.

Comparative Example 5
The same operation as in Example 5 was performed except that the aluminum oxide precursor sol 3 was changed to 1.
As a result, when the aluminum oxide precursor sol 1 was spin-coated, streaky unevenness extending radially from the center of the substrate to the periphery was confirmed. The difference in reflectance after immersion in warm water was 0.2%, confirming in-plane variation in antireflection properties.

Comparative Example 6
The same operation as in Example 5 was performed except that the aluminum oxide precursor sol 3 was changed to 2.
As a result, when the aluminum oxide precursor sol 2 was spin-coated, large star-shaped unevenness was confirmed at the center of the substrate. The difference in reflectance after immersion in warm water was 0.2%, confirming in-plane variation in antireflection properties.

Comparative Example 7
The same operation as in Example 5 was performed except that the aluminum oxide precursor sol 3 was changed to 7.
As a result, when the aluminum oxide precursor sol 7 was spin-coated, streaky unevenness extending radially from the center of the substrate to the periphery was confirmed. The difference in reflectance after immersion in warm water was 0.2%, and in-plane variation in antireflection properties was confirmed.

Comparative Example 8
The same operation as in Example 4 was performed except that the aluminum oxide precursor sol 3 was changed to 12.
As a result, when the aluminum oxide precursor sol 12 was spin-coated, streaky unevenness and innumerable cracks extending radially from the center of the substrate to the periphery were confirmed. The difference in reflectance after immersion in warm water was 0.2%, and in-plane variation in antireflection properties was confirmed.

Comparative Example 9
The same operation as in Example 7 was performed except that the aluminum oxide precursor sol 8 was changed to an average particle diameter and a peak area of 1.7 nm and 84%, respectively.
As a result, the result of measuring the reflectance is shown in FIG.

Comparative Example 10
The same operation as in Example 7 was performed except that the precursor was changed to the aluminum oxide precursor sol 9 (average particle diameter and peak area were 2.2 nm and 88%, respectively).

  As a result, the result of measuring the reflectance is shown in FIG.

(Note 1) * Catalyst water (molar equivalent) indicates the molar equivalent of catalytic water with respect to aluminum-sec-butoxide.
(Note 2) * Main peak area indicates the ratio of the peak area of the average particle diameter in the table to the total peak area.

[Performance evaluation]
From Examples 1 to 4, it was confirmed that the viscosity of the aluminum oxide precursor sols 3 to 6 having a particle size in a specific region was reduced and the by-products were reduced. Also, optical films with little variation in reflectance were obtained by using those aluminum oxide precursor sols from Examples 5 to 8. Further, in Examples 9 and 10, the effect of lowering the reflectance was also confirmed. On the other hand, in Comparative Examples 5 to 8, optical films having poor applicability of the aluminum oxide precursor sol and large variations in reflectance were obtained.

  The optical member manufactured according to the present invention can correspond to a transparent base material having an arbitrary refractive index, exhibits an excellent antireflection effect for visible light, and has long-term weather resistance. Various displays such as TVs and plasma display panels: Polarizing plates used in liquid crystal display devices, sunglasses lenses made of various optical glass materials and transparent plastics, prescription eyeglass lenses, camera finder lenses, prisms, fly-eye lenses, toric lenses, Optical members such as various optical filters and sensors: Furthermore, photographing optical systems using them, observation optical systems such as binoculars, projection optical systems used for liquid crystal projectors, etc .: various optical lenses such as scanning optical systems used for laser beam printers, etc. : Covers for various instruments, window glass for cars, trains, etc. It can be used for optical members.

DESCRIPTION OF SYMBOLS 1 Base material 2 Aluminum oxide precursor sol 3 Aluminum oxide film 4 Layer which has uneven structure of aluminum oxide boehmite 5 Uneven structure of aluminum oxide boehmite 6 Plate-like crystal formed from the plate-like crystal which has aluminum oxide boehmite as a main component Layer 7 Concave and convex shape 8 Inclination direction 9 Tangent line of substrate surface 10 Layer mainly composed of other than aluminum oxide

Claims (5)

A particle containing a hydrolyzate of an aluminum compound and / or a condensate thereof as a component, and a solvent,
Ri average particle diameter der than 7nm less 2.5nm of said particles,
The solvent contains 50 to 90% by weight of a monohydric alcohol having 5 to 8 carbon atoms and a water-soluble solvent having a boiling point of 110 to 170 ° C. in a proportion of 10 to 50% by weight. An aluminum oxide precursor sol.   The particle size distribution curve of the particles has at least one or more peaks having a single peak, the average particle diameter of one of the peaks being 2.5 nm or more and 7 nm or less, and the average particle diameter being 2.5 nm or more 2. The aluminum oxide precursor sol according to claim 1, wherein an area of a peak of 7 nm or less is 90% or more with respect to a total area of a particle size distribution curve. The aluminum oxide precursor sol according to claim 2, wherein the water-soluble solvent is glycol ether. The aluminum oxide precursor sol according to any one of claims 1 to 3 , wherein the particles are amorphous. (1) supplying the aluminum oxide precursor sol according to any one of claims 1 to 4 on at least one surface of the substrate;
(2) a step of spreading the aluminum oxide precursor sol on a substrate;
(3) a step of forming an aluminum oxide film by drying and / or firing the substrate;
(4) A method for producing an optical member, comprising a step of forming an uneven structure of aluminum oxide boehmite by immersing the aluminum oxide film in warm water of 60 ° C. or higher and 100 ° C. or lower.

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